Landslide Risk: Economic Valuation in the North-Eastern Zone of Medellin City

Natural disasters of a geodynamic nature can cause enormous economic and human losses. The economic costs of a landslide disaster include relocation of communities and physical repair of urban infrastructure. However, when performing a quantitative risk analysis, generally, the indirect economic consequences of such an event are not taken into account. A probabilistic approach methodology that considers several scenarios of hazard and vulnerability to measure the magnitude of the landslide and to quantify the economic costs is proposed. With this approach, it is possible to carry out a quantitative evaluation of the risk by landslides, allowing the calculation of the economic losses before a potential disaster in an objective, standardized and reproducible way, taking into account the uncertainty of the building costs in the study zone. The possibility of comparing different scenarios facilitates the urban planning process, the optimization of interventions to reduce risk to acceptable levels and an assessment of economic losses according to the magnitude of the damage. For the development and explanation of the proposed methodology, a simple case study is presented, located in north-eastern zone of the city of Medellín. This area has particular geomorphological characteristics, and it is also characterized by the presence of several buildings in bad structural conditions. The proposed methodology permits to obtain an estimative of the probable economic losses by earthquake-induced landslides, taking into account the uncertainty of the building costs in the study zone. The obtained estimative shows that the structural intervention of the buildings produces a reduction the order of 21 % in the total landslide risk. © Published under licence by IOP Publishing Ltd

Detailed and large-scale cost/benefit analyses of landslide prevention vs. post-event actions

The main aim of this paper is to test economic benefits of landslide prevention measures vs. post-event emergency actions. To this end, detailed- and large-scale analyses were performed in a training area located in the northeastern Italian pre-Alps that was hit by an exceptional rainfall event occurred in November 2010. On the detailed scale, a landslide reactivated after 2010 event was investigated. Numerical modeling demonstrated that remedial works carried out after the landslide – water-removal intervention such as a drainage trench – could have improved slope stability if applied before its occurrence. Then, a cost/benefit analysis was employed. It defined that prevention would have been economically convenient compared to a non-preventive and passive attitude, allowing a 30 % saving relative to total costs. On the large scale, one of the most affected areas after 2010 event was considered. A susceptibility analysis was performed using a simple probabilistic model, which allowed to highlight the main landslide conditioning factors and the most hazardous and vulnerable sectors. In particular, such low-cost analysis demonstrated that almost 50 % of landslides occurred after 2010 event could be foreseen and allowed to roughly quantify benefits from regional landslide prevention. However, a large-scale approach is insufficient to carry out a quantitative cost/benefit analysis, for which a detailed case-by-case risk assessment is needed. The here proposed approaches could be used as a means of preventive soil protection in not only the investigated case study but also all those hazardous areas where preventive measures are needed

VULNERABILITY MAPPING AND ANALYSIS: AN IMPLEMENTATION IN GEOHAZARD AREAS IN SABAH

Vulnerability identifies the element-at-risk as well as the evaluation of their relationships with the hazard. The relationships relate the landslide potential damages over a specific element-at-risk. Vulnerability can be defined as the degree of loss to a given element-at-risk or set of elements at risk resulting from the occurrence of a natural phenomenon of a given magnitude and expressed on a scale from 0 (no damage) to 1 (total damage). In this study, the landslide vulnerability mapping and analysis were made on two element-at-risks namely buildings and roads. Based on field observations, building and road construction materials have been classified into 22 and 5 construction materials respectively. The field visits were made on specific areas based on candidate buildings and roads as chosen during the landslide exposure analysis and mapping. The vulnerability values for these element-at-risks were expressed using expert opinion. Four experts have been interviewed with separate sessions. The experts were also supplied with local information on the landslides occurrences and photos of element-at-risk in Kundasang and Kota Kinabalu. The vulnerability matrices were combined based on the weighted average approach, in which higher weight was assigned to panel with local expert (landslides and damage assessment), wide experience in landslide vulnerability analysis, hazard and risk mapping. Finally, the vulnerability maps were produced for Kundasang and Kota Kinabalu with spatial resolution of 25 cm. These maps were used for the next step i.e. landslide risk mapping and analysis

3rd Probabilistic Workshop Technical Systems, Natural Hazards

Modern engineering structures should ensure an economic design, construction and operation of structures in compliance with the required safety for persons and the environment. In order to achieve this aim, all contingencies and associated consequences that may possibly occur throughout the life cycle of the considered structure have to be taken into account. Today, the development is often based on decision theory, methods of structural reliability and the modeling of consequences. Failure consequences are one of the significant issues that determine optimal structural reliability. In particular, consequences associated with the failure of structures are of interest, as they may lead to significant indirect consequences, also called follow-up consequences. However, apart from determining safety levels based on failure consequences, it is also crucially important to have effective models for stress forces and maintenance planning ... (aus dem Vorwort

From spatio-temporal landslide susceptibility to landslide risk forecast

The literature on landslide susceptibility is rich with examples that span a wide range of topics. However, the component that pertains to the extension of the susceptibility framework toward space–time modeling is largely unexplored. This statement holds true, particularly in the context of landslide risk, where few scientific contributions investigate risk dynamics in space and time. This manuscript proposes a modeling protocol where a dynamic landslide susceptibility is obtained via a binomial Generalized Additive Model whose inventories span nine years (from 2013 to 2021). For the analyses, the data cube is organized with a mapping unit consisting of 26,333 slope units repeated over an annual temporal unit, resulting in a total of 236,997 units. This phase already includes several interesting modeling experiments that have rarely appeared in the landslide literature (e.g., variable interaction plots). However, the main innovative effort is in the subsequent phase of the protocol we propose, as we used climate projections of the main trigger (rainfall) to obtain future estimates of yearly susceptibility patterns. These estimates are then combined with projections of urban settlements and associated populations to create a dynamic risk model, assuming vulnerability = 1. Overall, this manuscript presents a unique example of such a modeling routine and offers a potential standard for administrations to make informed decisions regarding future urban development.</p

Landslide riskscapes in the Colorado Front Range: a quantitative geospatial approach for modeling human-environment interactions

2021 Spring.Includes bibliographical references.This research investigated the application of riskscapes to landslides in the context of geospatial inquiry. Riskscapes are framed as a landscape of risk to represent risk spatially. Geospatial models for landslide riskscapes were developed to improve our understanding of the spatial context for landslides and their risks as part of the system of human-environment interactions. Spatial analysis using Geographic Information Systems (GIS) leveraged modeling methods and the distributed properties of riskscapes to identify and preserve these spatial relationships. This dissertation is comprised of four separate manuscripts. These projects defined riskscapes in the context of landslides, applied geospatial analyses to create a novel riskscape model to introduce spatial autocorrelation methods to the riskscape framework, compared geostatistical analysis methods in these landslide riskscape assessments, and described limitations of spatial science identified in the riskscape development process. The first project addressed the current literature for riskscapes and introduced landslides as a measurable feature for riskscapes. Riskscapes are founded in social constructivist theory and landslide studies are frequently based on quantitative risk assessment practices. The uniqueness of a riskscape is the inclusion of human geography and environmental factors, which are not consistently incorporated in geologic or natural hazard studies. I proposed the addition of spatial theory constructs and methods to create spatially measurable products. I developed a conceptual framework for a landslide riskscape by describing the current riskscape applications as compared to existing landslide and GIS risk model processes. A spatial modeling formula to create a weighted sum landslide riskscape was presented as a modification to a natural hazard risk equation to incorporate the spatial dimension of risk factors. The second project created a novel method for three geospatial riskscapes as an approach to model landslide susceptibility areas in Boulder and Larimer Counties, Colorado. This study synthesized physical and human geography to create multiple landslide riskscape models using GIS methods. These analysis methods used a process model interface in GIS. Binary, ranked, and human factor weighted sum riskscapes were created, using frequency ratio as the basis for developing a weighting scheme. Further, spatial autocorrelation was introduced as a recommended practice to quantify the spatial relationships in landslide riskscape development. Results demonstrated that riskscapes, particularly those for ranked and human factor riskscapes, were highly autocorrelated, non-random, and exhibited clustering. These findings indicated that a riskscape model can support improvements to response modeling, based on the identification of spatially significant clustering of hazardous areas. The third project extended landslide riskscapes to measurable geostatistical comparisons using geostatistical tools within a GIS platform. Logistic regression, weights of evidence, and probabilistic neural networks methods were used to analyze the weighted sum landslide riskscape models using ArcGIS and Spatial Data Modeler (ArcSDM). Results showed weights of evidence models performed better than both logistic regression and neural networks methods. Receiver Operator Characteristic (ROC) curves and Area Under the Curve validation tests were performed and found the weights of evidence model performed best in both posterior probability prediction and AUC validation. A fourth project was developed based on the limitations discovered during the analytical process evaluations from the riskscape model development and geostatistical analysis. This project reviewed the issues with data quality, the variations in results predicated on the input parameters within the analytical toolsets, and the issues surrounding open-source application tools. These limitations stress the importance of parameter selection in a geospatial analytical environment. These projects collectively determined methods for riskscape development related to landslide features. The models presented demonstrate the importance and influence of spatial distributions on landslide riskscapes. Based on the proposed conceptual framework of a spatial riskscape for landslides, weighted sum riskscapes can provide a basis for prioritization of resources for landslides. Ranked and human factor riskscapes indicate the need to provide planning and protection for areas at increased risk for landslides. These studies provide a context for riskscapes to further our understanding of the benefits and limitations of a quantitative riskscape approach. The development of a methodological framework for quantitative riskscape models provides an approach that can be applied to other hazards or study areas to identify areas of increased human-environment interaction. Riskscape models can then be evaluated to inform mitigation and land-use planning activities to reduce impacts of natural hazards in the anthropogenic environment

A simplified semi-quantitative procedure based on the SLIP model for landslide risk assessment: the case study of Gioiosa Marea (Sicily, Italy)

Landslide risk assessment is fundamental in identifying risk areas, where mitigation measures must be introduced. Most of the existing methods are based on susceptibility assessment strongly site-specific and require information often unavailable for damage quantification. This study proposes a simplified methodology, specific for rainfall-induced shallow landslides, that tries to overcome both these limitations. Susceptibility assessed from a physically-based model SLIP (shallow landslides instability prediction) is combined with distance derived indices representing the interference probability with elements at risk in the anthropized environment. The methodology is applied to Gioiosa Marea municipality (Sicily, south Italy), where shallow landslides are often triggered by rainfall causing relevant social and economic damage because of their interference with roads. SLIP parameters are first calibrated to predict the spatial and temporal occurrence of past surveyed phenomena. Susceptibility is then assessed in the whole municipality and validated by comparison with areas affected by slide movements according to the regional databases of historical landslides. It is shown that all the detected areas are covered by points where the SLIP safety factor ranges between 0 and 2. Risk is finally assessed after computation of distances from elements at risk, selected from the land use map. In this case, results are not well validated because of lack of details in the available regional hydrogeological plan, both in terms of extension and information. Further validation of the proposed interference indices is required, e.g., with studies of landslide propagation, which can also allow considerations on the provoked damage

A COLLABORATIVE WEB-GIS BASED DECISION SUPPORT PLATFORM FOR RISK MANAGEMENT OF NATURAL HAZARDS

L'un des principaux problèmes dans la gestion des risques est le manque de bonne communication et de collaboration efficace entre les services, agences et organisations chargés de la prévention, l'atténuation et la gestion des risques. La participation des différents groupes d'acteurs est une importante composante de la prévention et l'atténuation des risques. Cela demande une approche intégrée et coordonnée, qui aide les parties prenantes responsables de gérer le risque, depuis l'identification des risques jusqu'au processus de prise de décision, à obtenir la meilleure combinaison des stratégies de réduction des risques. Comme les dangers naturels et les risques liés à ces dangers sont de nature spatiale, les outils d'aide à la décision basés sur le web et intégrés aux systèmes d'informations géographiques (SIG, GIS en anglais] ont été considérés de plus en plus comme des instruments utiles. En prenant les avantages du web moderne, les technologies géospatiales et open-source pour obtenir une structure intégrée et centralisée, une plateforme collaborative web-SIG est proposée pour la gestion des risques avec la participation des différentes parties prenantes. Les principaux objectifs de cette recherche sont 1) de proposer une approche systématique et intégrée de gestion des risques avec la participation des différents parties prenantes; 2) d'étudier la possibilité et l'application des outils interactifs web-SIG d'aide à la décision pour l'analyse, la communication et l'échange d'informations entre les parties prenantes de la gestion des risques and 3) de proposer une approche novatrice pour améliorer potentiellement les activités de collaboration entre les parties prenantes grâce à des approches interactives et participatives. Les apports conceptuels de cette étude sont basés sur les premiers feedback, les entretiens semi- structurés et les observations obtenues lors des visites sur le terrain et des réunions avec les parties prenantes menées sur trois sites d'études en Europe, dans les régions de Voïvodie en Pologne, de Buzâu en Roumanie et du Frioul-Vénétie julienne en Italie. Même si certaines plates-formes existent dans les zones d'études, aucune n'a une plate-forme qui permet une approche flexible et collaborative pour formuler et la sélectionner des mesures de gestion des risques comme ce qui est tenté dans cette étude. De plus, la plupart des plates-formes existantes sont principalement concentrées sur l'inventaire des événements, la visualisation des risques et la diffusion de l'information. Dans cette recherche, un prototype est réalisé et centré sur l'analyse des risques, la formulation et la sélection des mesures potentielles en utilisant une interface interactive web-SIG intégrée à un outil d'évaluation multicritères (MCE). Cette plate-forme est considérée non seulement comme une plate-forme web pour le partage centralisé des informations des risques, mais aussi comme un outil pour assurer un cadre intégré où les parties prenantes concernées peuvent analyser les risques et évaluer les mesures de réduction des risques. Pour le développement du prototype, une architecture client-serveur à trois niveaux renforcée par Boundless (OpenGeo) a été appliquée avec son environnement de développement côté client. Ce prototype a été présenté aux parties prenantes locales et régionales des zones d'études. Leur feedback a été collecté pour comprendre leurs points de vue et déterminer si la plate-forme est utile et applicable pour leurs activités en matière de gestion des risques. Le prototype a également été évalué avec les étudiants pour obtenir des commentaires sur les différents aspects de la plate-forme et pour analyser la façon dont l'application des outils interactifs pourrait aider les étudiants à analyser et comprendre la gestion des risques. -- A collaborative web-GIS based décision support platform for risk management of natural hazards (Aye Zar Chi, ISTE) One of the main problems in risk management is the lack of good communication as well as efficient and effective collaboration between the agencies, services and organizations in charge of risk prévention, mitigation and management. The involvement of various stakeholder groups is an important component of risk prévention and mitigation. This calls for an integrated and coordinated approach which helps responsible stakeholders in managing risk, starting from risk identification to the decision-making process for achieving the best combination of risk réduction stratégies. As natural hazards and associated risks are spatial in nature, web-based décision support tools integrated with Géographie information systems (GIS) have been increasingly considered as useful instruments for providing décision support. Taking the advantages of modem web, spatial and open-source technologies to achieve a centralized and integrated framework, in this research, a web-GIS based collaborative décision support platform is proposed for risk management with involvement of various stakeholders. The principal purposes of this research are: (1) to conduct a systematic and integrated risk management approach with diverse involvement of différent stakeholders; (2) to explore the possibility and application of interactive web- GIS décision support tools for the analysis, communication and exchange of décision support information between risk management stakeholders and (3) to propose an innovative approach to potentially enhance collaboration activities between stakeholders through interactive and participatory approaches. The conceptual inputs of this study are based on the initial feedback, semi-structured interviews and observations obtained from the field visits and stakeholder meetings carried out in three case studies of Europe: the Malopolska Voivodeship of Poland, Buzâu County of Romania and the Friuli-Venezia-Giulia région of Italy. Even though some platforms exist in study areas, no single case has a platform at hand which enables as flexible and collaborative approach for the formulation and selection of risk management measures as attempted in this study. Moreover, most platforms have focused mainly on inventoiy of events, risk visualization and dissémination of information. In this research, a prototype is realized and focused on the risk analysis, formulation and selection of potential measures through the use of an interactive web-GIS based interface integrated with a Multi-Criteria Evaluation (MCE) tool. This platform is regarded not only as a web platform for centralized sharing of risk information but also for ensuring an integrated framework where involved stakeholders can analyse risk and evaluate risk réduction measures. For the prototype development, a three-tier client-server architecture backed up by Boundless (OpenGeo) was applied with its client side development environment. This developed prototype was presented to the local and régional stakeholders of the study areas and feedback was collected to understand their perspective in determining whether the platform is useful and applicable for their activities in risk management. The prototype was also further evaluated with students to obtain feedback on différent aspects of the platform as well as to analyse how the application of interactive tools could assist students in studying and understanding risk management

Short communication: A model to predict flood loss in mountain areas

Because effects of climate change and an increase in elements at risk, mountain hazard loss increased throughout Europe. Yet, factors influencing loss, i.e. vulnerability, have gained less attention to date. Vulnerability is defined as the degree of loss resulting from the hazard impact on buildings. Recent studies have focused on evaluating vulnerability to dynamic flooding using proxies from case studies and based on empirical ex-post approaches. However, the transferability to other case studies and, therefore, the ability of such models to actually predict future losses is limited. To overcome this gap, we present a beta model based on loss data from the European Alps, which clearly shows that a single vulnerability function is sufficient to predict losses resulting from different types of torrential hazards and to provide probabilities of destruction under specific scenarios. As a result, the curves are transferable and may significantly increase the predictive power of risk analyses

Digital image correlation (DIC) analysis of the 3 December 2013 Montescaglioso landslide (Basilicata, Southern Italy). Results from a multi-dataset investigation

Image correlation remote sensing monitoring techniques are becoming key tools for providing effective qualitative and quantitative information suitable for natural hazard assessments, specifically for landslide investigation and monitoring. In recent years, these techniques have been successfully integrated and shown to be complementary and competitive with more standard remote sensing techniques, such as satellite or terrestrial Synthetic Aperture Radar interferometry. The objective of this article is to apply the proposed in-depth calibration and validation analysis, referred to as the Digital Image Correlation technique, to measure landslide displacement. The availability of a multi-dataset for the 3 December 2013 Montescaglioso landslide, characterized by different types of imagery, such as LANDSAT 8 OLI (Operational Land Imager) and TIRS (Thermal Infrared Sensor), high-resolution airborne optical orthophotos, Digital Terrain Models and COSMO-SkyMed Synthetic Aperture Radar, allows for the retrieval of the actual landslide displacement field at values ranging from a few meters (2–3 m in the north-eastern sector of the landslide) to 20–21 m (local peaks on the central body of the landslide). Furthermore, comprehensive sensitivity analyses and statistics-based processing approaches are used to identify the role of the background noise that affects the whole dataset. This noise has a directly proportional relationship to the different geometric and temporal resolutions of the processed imagery. Moreover, the accuracy of the environmental-instrumental background noise evaluation allowed the actual displacement measurements to be correctly calibrated and validated, thereby leading to a better definition of the threshold values of the maximum Digital Image Correlation sub-pixel accuracy and reliability (ranging from 1/10 to 8/10 pixel) for each processed dataset